ERA = (earned runs ÷ innings pitched) × 9. It represents how many earned runs a pitcher would allow per nine-inning game. MLB average ERA varies by era — typically 3.80-4.50 in modern baseball. Below 3.00 is excellent; 3.00-3.80 is above average; above 4.50 is below average. ERA+ adjusts ERA for ballpark and league context (100 = exactly league average; 150 = 50% better). ERA can be inflated by bad fielding, which is why FIP (Fielding Independent Pitching) isolates pitching from defence.
Key points
- Earned runs / IP × 9
- MLB modern avg ~3.80-4.50
- ERA+ normalises for park and era
- FIP removes fielder influence
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